A rolling cone cutter earth boring bit consists of a main bit body adapted to be connected to a rotary drill string. The bit includes individual rotatable cone cutters mounted on individual bearing pins extending from the main bit body. Bearing systems are provided between the rolling cone cutters and the bearing pins to promote rotation of the cutters and means are provided on the outer surface of the cone cutters for disintegrating the earth formations as the bit and the cutters rotate. A sufficient supply of uncontaminated lubricant should be maintained proximate the bearing systems throughout the lifetime of the bit. Various forms of seals have been provided between the cone cutters and the bearing pins upon which they are mounted to retain lubricant and prevent contamination; however, the need for new sealing systems is as acute today as any time in the history of rock drilling.
A rolling cone cutter earth boring bit must operate under very severe conditions, and the size and geometry of the bit is restricted by the operating characteristics. At the same time, a longer lifetime and improved performance is needed from the bit. In attempting to provide an improved bit, new and improved materials have been developed for the cutting structure of the cone cutters. They have provided a longer useful lifetime for the cone cutters. This has resulted in the bearing systems of the bit being often the first to fail during the drilling operation. Consequently, a need exists for new and improved bearing systems to extend the useful lifetime of the bit and to allow development of other elements that interact with the sealing and bearing systems. In attempting to improve the bearing systems, various seal systems have been provided to maintain the bearing area free of harmful materials and retain lubricant. In attempting to provide new sealing systems, great care must be taken that the overall capacity of the bearing systems is not reduced.
In order to more fully appreciate the problems involved in providing new sealing systems for rolling cone earth boring bits, the following factors should be borne in mind. Relatively loose manufacturing tolerances inherently necessary in bit bearing assemblies create sealing problems that have not been satisfactorily solved. Tolerance requirements also present problems because of the tight fitting requirements. The bit bearings should be a maximum size to withstand the very heavy loads imposed while at the same time yielding to the hole size limitations specified by the user. A dilemma of adapting a maximum capacity bearing in a minimum of space is produced. This dilemma invariably leads to compromises which circumvent many of the well known requirements for proper assembly and use of high precision elements. This tolerance accumulation, though reasonable, is still far too much for effective operation of many forms of shaft seals. Extrusion and nibbling of elastomer seals in the gap between the rolling cone cutter and the bit body and eccentric rotation of the rolling cone cutter on the bearing pin are believed to reduce seal life.